The present invention pertains generally to chemical lasers that use Iodine gas as an input stream. More particularly, the present invention pertains to systems for producing Iodine gas and delivering the Iodine gas to a laser cavity. The present invention is particularly, but not exclusively, useful as an on-demand Iodine gas supply system that does not require a liquid Iodine reservoir to be maintained during periods of non-demand.
The Chemical-Oxygen-Iodine-Laser (COIL) is potentially useful for both military and commercial applications because it is capable of producing a high power laser beam. In the COIL process, Iodine gas is combined with singlet delta Oxygen in a laser cavity to produce a laser beam. Iodine, however, is a solid at room temperature. It must therefore be vaporized to produce the Iodine gas required in the COIL laser cavity.
One method for producing Iodine gas involves melting Iodine in an Iodine reservoir. The Iodine vapors that are given off by the molten Iodine are then transported using a carrier gas to the laser cavity through a delivery system. In general, the required delivery system involves piping and other complex parts such as valves, precision orifices, and temperature and pressure instruments. Unfortunately, this method of producing gaseous Iodine has several drawbacks. For instance, the entire delivery system, including the carrier gas, must be preheated and maintained at elevated temperatures to prevent Iodine condensation from plugging the delivery system. For a typical COIL system that is designed for military applications, several hours are required to melt the Iodine and preheat the delivery system. On the other hand, the source for generating the singlet delta Oxygen that is to be combined with the Iodine gas requires only a fraction of a minute to reach operational status.
In the molten and gaseous states, Iodine is extremely corrosive. Because of Iodine""s corrosivity, equipment exposed to Iodine, such as the Iodine reservoir and delivery system described above, must be fabricated from expensive materials such as Hastelloy C-276. In addition to degrading any exposed equipment, the corrosion reaction will, with time at temperature, contaminate the Iodine in the reservoir, requiring the Iodine in the reservoir to be periodically purified or discarded. Impurities in the Iodine must be maintained at very low levels as they may be transported to the laser cavity where they can coat the optical components. For military applications, where readiness is important, a reservoir of molten Iodine would be required at all times, leading to a significant amount of corrosion. Furthermore, the delivery system valves, which must be operated hot and in the presence of Iodine will deteriorate with time at temperature and leak allowing corrosive Iodine to escape. Such a leak could be potentially harmful to electronic equipment. For these reasons, in order to perform routine maintenance on the molten Iodine reservoir and delivery system, these systems must be periodically shut down and allowed to cool. Additionally, maintenance of liquid Iodine systems creates a large amount of Iodine contaminated waste that requires special handling and disposal. In summary, the molten Iodine reservoir and delivery system is large, heavy, costly and complex.
In light of the above, it is an object of the present invention to provide an on-demand Iodine gas supply system for a chemical laser that does not require a liquid Iodine reservoir to be maintained during periods of non-demand. It is another object of the present invention to provide an on-demand Iodine gas supply system for a chemical laser that does not require an Iodine delivery system to be maintained at an elevated temperature during periods of non-demand. It is still another object of the present invention to provide an on-demand Iodine gas supply system for a chemical laser that does not require a delivery system that contains complex parts such as valves and precision orifices. It is yet another object of the present invention to provide an on-demand Iodine gas supply system that allows system maintenance operations to be performed quickly and without generating a large amount of Iodine contaminated waste. Yet another object of the present invention is to provide an on-demand Iodine gas supply system which is easy to use, relatively simple to implement, and comparatively cost effective.
The present invention is directed to a system for supplying Iodine gas to a laser cavity. For the present invention, the system includes a cartridge for generating Iodine gas, and delivery piping for transporting Iodine from the cartridge to the laser cavity. The cartridge includes a substantially non-combustible casing that can be formed as a hollow cylinder that is open at one end and closed at the other. In accordance with the present invention, the delivery piping is attached to the open end, placing the delivery piping in fluid communication with the inside of the casing. A solid purge material is disposed in the casing and extends from the closed end of the casing to a first interface. For the present invention, the purge material preferably consists of an Iodine-free, solid material that produces a relatively inert gas when ignited.
The cartridge also includes a solid mixture of fuel and oxidizer. Importantly, the mixture contains Iodine. For the present invention, the mixture containing Iodine is disposed in the casing to extend from the first interface to a second interface. With this combination of structure, the mixture containing Iodine is in direct contact with the purge material at the first interface. A preferred mixture for the present invention includes a stoichiometric amount of C2I4 fuel and Iodine Pentoxide (I2O5) oxidizer. Optionally, the mixture can include solid Iodine. Preferably, the mixture is compounded to produce a gas having molecular Iodine as its major constituent when ignited.
In addition to the solid mixture containing Iodine and the solid purge material, the cartridge also preferably includes an Iodine-free, solid preheat material. The preheat material is disposed in the casing and extends from the second interface to a third interface. As such, the preheat material and the mixture containing Iodine are in direct contact with each other at the second interface. For the present invention, the preheat material can be any suitable material that produces an elevated temperature gas when ignited.
The cartridge also includes an ignitor squib that is disposed in the casing near the open end of the casing, and is in direct contact with the preheat material. With this combination of structure, the ignitor squib can be activated to initiate a burn front that travels sequentially through the preheat material, the mixture containing Iodine and the purge material. As the burn front passes through the preheat material, gases at elevated temperatures are generated that exit the cartridge through the open end of the casing and flow through the delivery piping. These hot gases heat the delivery piping to a temperature sufficient to prevent Iodine gas condensation in the piping.
Next, with the preheat material vaporized and removed from the casing, the burn front passes through the mixture containing Iodine, igniting the mixture and generating Iodine gas. The Iodine gas then exits the casing through the open end and flows through the preheated delivery piping to the laser cavity. It is to be appreciated that the flow rate of Iodine gas and the period of Iodine gas generation can be selectively altered by varying the dimensions of the solid mixture and the casing. Specifically, the length is proportional to the delivery time and the cross sectional area is proportional to the Iodine flow rate. In the laser cavity, the Iodine gas can be used to create a laser beam. For example, in the well known chemical-Oxygen-Iodine-laser (COIL) process, Iodine gas is combined with singlet delta Oxygen in the laser cavity to produce a laser beam. The present invention can also be used as an Iodine on-demand system for an All Gas Iodine Laser (AGIL).
Once the burn front has traversed the mixture containing Iodine and the entire mixture is vaporized and removed from the casing, the burn front passes through the purge material, igniting the purge material and generating a purge gas. The purge gas then exits the casing through the open end and flows through the delivery piping to remove any traces of corrosive Iodine from the delivery piping.